A conventional non-brush D.C. motor includes a stator having a plurality of poles, and a housing receiving hole at its center. Each pole is shaped as a T character and a group of coils is wound around every arm of the poles. The costs for the stator and the wound coils are very expensive.
According to the prior art of U.S. Pat. No. 4,987,331, another conventional non-brush D.C. motor is provided. The non-brush D.C. motor with an improved stator is constituted by a base made of plastic materials, a coil winding around the base, two sets of magnetic polar plates each set of which forming a pair of magnetic poles fixed at both sides of the base, and a circuit board connected to one side of the base. The two sets of polar plates are staggered each other. For the stator with this staggered structure, the magnet of the rotor must correspondingly be a strip which is magnetized radially and has the N and S polarities arranged spacedly.
The structure of the above improved motor is quite different from the common motors. The rotor is a magnet of a strip which is magnetized radially and has the N and S polarities arranged spacedly. The bobbin within the coil and the polar plates magnetically connected to a metal bushing constitutes the improved stator. The two polar plates form a staggered position with each other by one pole. The upper polar plate is piled by multiple layers of silicon steel, and the lower polar plate is also piled by the same layers of silicon steel. When the coil is excited to generate magnetic field, with the help of the magnetic polar plates the metal bushing generates magnetic field so that the shaft of the rotor can be rotated.
For the two sets of magnetic polar plates, each set has a pair of the magnetic poles. However, this structure leads to a larger size of the stator structure. Besides, the two set of the magnetic polar plates which are staggered each other lower the efficiency of the motor.
Accordingly, it is necessary to provide a more compact and stable rotor and stator structure for improving the efficiency of the motor.